6.1.2.4. Example Code

Overview

Full documentation for creating an OGSA-DAI client is available in the OGSA-DAI documentation. This page aims to provide a simple example to get started with the OGSA-DAI client library.

The GRIA OGSA-DAI service has several endpoints. The most important ones are the service itself (OgsaDaiServiceI2) for use with the GRIA API and OgsaDaiSubscription endpoint that presents itself as an OGSA-DAI service.

Before trying this example remember to follow the instructions on configuring an OGSA-DAI client.

import java.sql.ResultSet;


import uk.ac.soton.itinnovation.grid.client.ogsadai.OgsaDaiSSLHelper;
import uk.org.ogsadai.client.toolkit.GenericServiceFetcher;
import uk.org.ogsadai.client.toolkit.ResourceID;
import uk.org.ogsadai.client.toolkit.Response;
import uk.org.ogsadai.client.toolkit.activity.ActivityRequest;
import uk.org.ogsadai.client.toolkit.activity.sql.SQLQuery;

import uk.org.ogsadai.client.toolkit.activity.sql.WebRowSet;
import uk.org.ogsadai.client.toolkit.properties.DAIVersion;
import uk.org.ogsadai.client.toolkit.service.DataService;


public class Test
{
  public static void main(String[] args)
  {
    try

    {
      // Loads the keystore specified in the crypto.properties file
      // This only needs to be done once on application startup.
      OgsaDaiSSLHelper.setupKeystore();

      // This is the URL of the GRIA OGSA-DAI service
      String handle = "https://www.changeme.com:8443/gria-ogsadai-service/services/OgsaDaiSubscription";
      
      DataService service = GenericServiceFetcher.getInstance().getDataService(handle, null);
      
      // Fetch the OGSA-DAI version
      DAIVersion version = service.getVersion();
      System.out.println("Version: " + version.getMajorVersion() + "." + version.getMinorVersion());
      
      // Get a list of data resources we can access

      // This will return our database subscriptions
      // (those for which we have the "owner" or "client" role)
      ResourceID[] resources = service.getResourceIDs();
      for (int i=0; i<resources.length; i++)
      {
        System.out.println(resources[i].getName());
      }
      
      if (resources.length < 1)
        return;
      
      // In this example we shall perform a query on the first subscription that is returned

      service.setResourceID(resources[0]);
      
      // Create a query to list the tables in the database
      SQLQuery query = new SQLQuery("show tables");
      WebRowSet rowset = new WebRowSet(query.getOutput());
      
      ActivityRequest request = new ActivityRequest();
      request.add(query);
      request.add(rowset);
      
      // Perform the request

      Response response = service.perform(request);
      
      // Get and display the results
      ResultSet result = rowset.getResultSet();
      while (result.next())
      {
        String tableName = result.getString(1);
        System.out.println(tableName);
      }
    }
    catch (Throwable e)
    {
      e.printStackTrace();
    }
  }
}

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